1. Field of the Invention
The present invention relates generally to an apparatus and a method for providing synchronized data by using visible Light Emitting Diode (LED) lighting, and more particularly to an apparatus and a method for providing synchronized data without collision between LED lightings by using a mobile communication network.
2. Description of the Related Art
The Korean Ministry of Commerce, Industry and Energy (the present Ministry of Knowledge Economy) advised that the present manner of lighting would be replaced by LED lighting by 2015. In recent days, the luminous efficiency of LED lighting has improved, and the cost has dropped. Therefore, the LED lighting is becoming more common in the general lighting market such as the fluorescent lamp market, incandescent lamp market, and the like, as well as the specialty lighting market, such as the market for special lights used in mobile devices, displays, vehicles, traffic lights, and advertising boards, and the like. Also, due to the depletion of Radio Frequency (RF) band frequencies, possible confusion between various wireless communication technologies, the increase in demand for secure communication, the advent of 4th generation wireless technology, and the like, interest in light-wireless technology which operates alongside RF technology has recently increased. Therefore, research into visible light wireless communication using visible light LED lighting has progressed in various enterprises, research institutes, etc.
The advantage of visible light communication for delivering information is that it is safe, has a wide usable band, and can be freely used without regulation. Moreover, since a user can see a place where the visible light reaches or a direction in which the visible light travels, he/she can accurately recognize the reception range of information. In this regard, the visible light communication is reliable in an aspect of security, and can also be operated with low power in an aspect of power consumption. Therefore, the visible light communication can be applied to hospitals, airplanes, etc., having limitations on the use of RF. Also, it can provide an additional information service using an electric billboard. A system for the visible light communication having the above advantages will be described with reference to drawings below.
FIG. 1 is a diagram illustrating the configuration of a communication system using conventional Visible Light Communication (VLC). A regular VLC system includes first and second LED lightings 101 and 102, and mobile terminals 120 and 121. First and second LED lightings 101 and 102 include LED lightings, and perform data transmission/reception by using visible light simultaneously with the role of lighting. Mobile terminals 120 and 121 include visible light transmission/reception modules, and transmit/receive data to/from first and second LED lightings 101 and 102. Each of the communication areas of first and second LED lightings 101 and 102 is the same as the relevant lighting area. Therefore, at least one mobile terminal located in the relevant lighting area can receive a signal. First and second LED lightings 101 and 102 may randomly select time slots, and transmit information during the randomly-selected time slots. Other than this, each LED lighting may select a time slot based on a preset IDentification (ID), and transmit information during the selected time slot. Mobile terminals 120 and 121 include mobile phones, Personal Digital Assistants (PDA), smart phones, etc.
However, LED lighting cannot synchronize with another LED lighting adjacent to it. Accordingly, even though information is transmitted in an area where two lightings overlap, the possibility of collision becomes higher in a reception unit of a mobile terminal. FIG. 2 is a diagram illustrating the execution of transmitting data during a time slot, which has been randomly selected, by the conventional LED lighting. As illustrated in FIG. 2, adjacent LED lighting lamps 1 and 2, when a time slot is randomly selected and data is then transmitted during the time slot, a reception unit of a mobile terminal simultaneously receives data from two lighting lamps, so that collision may occur. Even when a time slot is selected based on an ID of the relevant LED lighting, it is not possible to know an ID of another LED lighting adjacent to the relevant LED lighting. Therefore, the same time slot period may be selected. Due to this, collision may occur.
In order to prevent the problems described above, it is possible to use a VLC system for providing data by combining power line communication based on power lines with LED lightings inside a building. However, for the VLC system as above, all LED lightings located in the building are connected to power lines, placing a server for controlling the power line communication as the center. As a result, problems arise in that the implementation of the VLC system itself is not easy, and the installation cost becomes expensive.
Therefore, there has been a demand for a method capable of synchronizing adjacent LED lightings without using a system such as the power line communication.